This invention relates, in general, to semiconductor devices and, more particularly, to a means and method for providing an integrated photosensor for semiconductor integrated circuits in a fashion compatible with the methods and structures used for such integrated circuits.
Integrated circuits containing thousands to millions of transistors and other elements are commonplace today. These integrated circuits operate at such high speeds that the propagation time of signals from one part to another of the integrated circuit chip or from one integrated circuit chip to another are of concern. For these and other reasons there is great interest in providing optical devices within integrated circuits so that signals may be coupled optically rather than electrically.
It is known in the prior art to provide optical coupling to integrated circuits by a hybrid approach, that is, using separately constructed optical sensors which are mounted on or near a semiconductor die containing the circuitry intended to use the optically received signal and then connecting the sensor die and the integrated circuit die by wire bonding, tab bonding, solder bumps, or the like. This approach has the advantage of allowing the optical device and the integrated circuit to be individually optimized so far as their manufacturing and electrical characteristics are concerned. However, when very small optical devices are needed for use in connection with highly complex and dense modern day integrated circuits, this hybrid approach is no longer satisfactory. Thus, there is an ongoing need for means and methods for constructing high performance optical sensors on the same substrate and at the same time as the semiconductor integrated circuit to which it is electrically coupled and of small dimension.
Accordingly, it is an object of the present invention to provide a means and method for forming a photodetector as part of an integrated circuit.
It is a further object of the present invention to provide a means and method for forming a photodetector as part of an integrated circuit using compatible fabrication methods and structure.
It is an additional object of the present invention to provide a means and method for forming a photodetector as part of an integrated circuit using compatible fabrication methods and structure and which has high sensitivity and performance at the low voltages commonly used for integrated circuits, especially with high speed and high density bipolar integrated circuits.
As used herein the word "intrinsic" in connection with semiconductor materials is intended to refer to semiconductor materials of either conductivity type having a resistivity greater than about one hundred ohm-cm.